Hhhmmmm...well I don't think anywhere that close to DC actually got below 0F. "Rock Creek Park" officially stops inside the city. At any rate no gardenia is going to truly be zn 6 hardy and obviously the existing so-called hardy ones are only hardy for mild-to-moderate zn 7a conditions.

I had both 'Kleim's Hardy' and a smaller 'Chuck Hayes'; considering the CH was much younger it died no more quickly, maybe even a bit less quickly. But by the, what was it, 5 or 6th round of record low temps in early March, they were both dead. Both would have been fine with the first drop to 3F if it had been the only one, and the KH had almost never been injured before. I'll probably just replace at some point w/CH, since the flowers are a little showier and no less fragrant. But they are both still deserving shrubs in the DC area IMHO, dying once every 20 years is manageable for a shrub if you don't mind the replacement cost and aren't using it as a "foundation" shrub. (OMG honey, our house lost its foundations! We'll have to move!)

This post was edited by davidrt28 on Tue, May 20, 14 at 5:28

Had two new ones this year, Klehm's Hardy sitting in the pot this cold, cold winter and Chuck Hayes planted in the fall. The Kleim's Hardy made it (it was purchased at 1/3 of the size of the other one) and the Chuck Hayes croaked. Go figure. Apparently, it really is true that if you neglect a gardenia, it's much happier.

I am in Northern VA. Had a 'Chuck Hayes' that is still alive but lost all of its leaves and has not put out any recovery growth. I potted it up for now.

I think Chuck is my favorite of the hardy gardenia cultivars. I also like 'Frost Proof' (smaller leaves than species) and one called 'Summer Snow' ('Chuck Hayes' X 'Kleim's Hardy' hybrid with large double flowers) which is supposed to be hardy to Zone 6.

However, keeping it in a pot (even a large one) rather than in the ground will significantly reduce its hardiness. Zone ratings all operate under the assumption that the plant is in the ground. The ground provides a great deal of warmth during winter. In a pot, the roots will essentially be the same temp as the air. Therefore, I don't think I would try a hardy gardenia cultivar in a pot unless you can move the pot to a protected location during winter (e.g., a garage or basement).